The ribosomes of the rough endoplasmic reticulum are targeted to the cytoplasmic side of the membrane via
A) a signal sequence within the 28S ribosomal RNA.
B) a sequence within the protein being synthesized.
C) the S6 ribosomal protein.
D) the cap sequence at the 5′ end of the mRNA being translated.

Question

Quizplus · Accepted Answer

The signal sequence within the protein being synthesized directs ribosomes to the rough endoplasmic reticulum. This signal sequence is recognized by a signal recognition particle (SRP) that binds to the ribosome and directs it to the ER membrane. The SRP binds to a receptor on the ER membrane, allowing the ribosome to dock and begin protein synthesis into the lumen of the ER.

The Ribosomes of the Rough Endoplasmic Reticulum Are Targeted to the Cytoplasmic